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docker Images

Use from docker hub​

https://hub.docker.com/

一個 image 可以有多個 tag

不指定版號，會自動下載最新版 docker pull nginx

要下載指定 version image docker image nginx:1.11.9

alpine 版本通常很小，alpine 本身小於 5MB。用於 linux 分散式系統？？？？。

docker hub -> The apt package system for container.

docker image cache​

  • image layers old: docker history nginx new: docker image history nginx

    list history of the image layers. Every image starts from the very beginning with a blank layer known as scratch.

IMAGE          CREATED       CREATED BY                                      SIZE      COMMENT
c919045c4c2b   2 weeks ago   /bin/sh -c #(nop)  CMD ["nginx" "-g" "daemon…   0B
<missing>      2 weeks ago   /bin/sh -c #(nop)  STOPSIGNAL SIGQUIT           0B
<missing>      2 weeks ago   /bin/sh -c #(nop)  EXPOSE 80                    0B
<missing>      2 weeks ago   /bin/sh -c #(nop)  ENTRYPOINT ["/docker-entr…   0B
<missing>      2 weeks ago   /bin/sh -c #(nop) COPY file:09a214a3e07c919a…   4.61kB
<missing>      2 weeks ago   /bin/sh -c #(nop) COPY file:0fd5fca330dcd6a7…   1.04kB
<missing>      2 weeks ago   /bin/sh -c #(nop) COPY file:0b866ff3fc1ef5b0…   1.96kB
<missing>      2 weeks ago   /bin/sh -c #(nop) COPY file:65504f71f5855ca0…   1.2kB
<missing>      2 weeks ago   /bin/sh -c set -x     && addgroup --system -…   61.1MB
<missing>      2 weeks ago   /bin/sh -c #(nop)  ENV PKG_RELEASE=1~bullseye   0B
<missing>      2 weeks ago   /bin/sh -c #(nop)  ENV NJS_VERSION=0.7.2        0B
<missing>      2 weeks ago   /bin/sh -c #(nop)  ENV NGINX_VERSION=1.21.6     0B
<missing>      2 weeks ago   /bin/sh -c #(nop)  LABEL maintainer=NGINX Do…   0B
<missing>      2 weeks ago   /bin/sh -c #(nop)  CMD ["bash"]                 0B
<missing>      2 weeks ago   /bin/sh -c #(nop) ADD file:d48a85028743f16ed…   80.4MB
  • union file system
  • history and inspect commands old: docker inspect nginx new: docker image inspcet nginx
  • copy on write

Images are made up of file system changes and metadata. Each Layer is uniquely identified and only stored once on a host. This saves storage space on host and transfer time on push/pull. A container is just a single read/write layer on top of image.

Image tagging and pushing to Docker hub​

  • Assign one or more tags to an image old: docker tag <source_image>[:tag] <new_image>[:tag] new: docker image tag <source_image>[:tag] <new_image>[:tag]

    <user>/<repo>:<tag>

    official Repositories => the live at the root namespace of the registry, so the don't need account name in front of repo name.

  • Uploads changed layers to a image registry (default is hub) docker image push <image>

  • Default to logging in Hub, but you can override by adding server url docker login <server>

    put in .docker/config.json

  • Always logout from shared machines or servers when done, to protect your account dcoker logout

    • Image id 會決定倉庫上的 image 是否為同一個，若 tag 不同，仍然會視為同一 image.

Building Image​